The present invention relates to a membrane intended to close and form part of the external wall of a reservoir which is capable of being implanted under the skin of a patient. The membrane may also be used elsewhere as desired, wherever strength and flexibility are needed.
Such reservoirs are well-known, for example see French Patent Publication No. 2,582,222, corresponding to U.S. Pat. No. 4,718,894. These reservoirs are generally made of a hollow, rigid body closed by one or two membranes defining, with the body, a chamber of variable volume.
At least one other membrane or other barrier, typically of smaller size than the closure membrane, is generally mounted on the body in addition to the preceding membrane or membranes, to provide an injection site for filling the reservoir.
Also, a pump with manual, electronic, or electromechanical control allows a dose of the liquid contained in the reservoir to be transferred to a catheter which terminates at a predetermined site in the body of the patient.
When the assembly has been implanted under the skin of the patient, with the closure and filling membranes on the exterior side, the reservoir may be regularly filled using an injection syringe, the needle of which is successively caused to pass through the patient's skin and the membrane of the injection site.
Once the reservoir is filled, the patient can then himself deliver the medicament contained in the reservoir to the chosen site, with the aid of the pump.
It is, however, essential that the person carrying out the filling of the reservoir penetrates the injection site membrane, and not a closure membrane of the reservoir or a pump control.
The present invention aims to provide a membrane which is not perforable by a hypodermic needle, and nevertheless retains all the characteristics required of such a membrane, for example its flexibility, allowing variation in the volume of the chamber. Also, the membrane of this invention can prevent diffusion of substances of low molecular weight, and exhibits good biocompatibility.